mktag.c

   1 #include "cache.h"
   2 #include "tag.h"
   3 #include "exec_cmd.h"
   4
   5 /*
   6  * A signature file has a very simple fixed format: four lines
   7  * of "object <sha1>" + "type <typename>" + "tag <tagname>" +
   8  * "tagger <committer>", followed by a blank line, a free-form tag
   9  * message and a signature block that git itself doesn't care about,
  10  * but that can be verified with gpg or similar.
  11  *
  12  * The first four lines are guaranteed to be at least 83 bytes:
  13  * "object <sha1>\n" is 48 bytes, "type tag\n" at 9 bytes is the
  14  * shortest possible type-line, "tag .\n" at 6 bytes is the shortest
  15  * single-character-tag line, and "tagger . <> 0 +0000\n" at 20 bytes is
  16  * the shortest possible tagger-line.
  17  */
  18
  19 /*
  20  * We refuse to tag something we can't verify. Just because.
  21  */
  22 static int verify_object(unsigned char *sha1, const char *expected_type)
  23 {
  24         int ret = -1;
  25         enum object_type type;
  26         unsigned long size;
  27         void *buffer = read_sha1_file(sha1, &type, &size);
  28
  29         if (buffer) {
  30                 if (type == type_from_string(expected_type))
  31                         ret = check_sha1_signature(sha1, buffer, size, expected_type);
  32                 free(buffer);
  33         }
  34         return ret;
  35 }
  36
  37 #ifdef NO_C99_FORMAT
  38 #define PD_FMT "%d"
  39 #else
  40 #define PD_FMT "%td"
  41 #endif
  42
  43 static int verify_tag(char *buffer, unsigned long size)
  44 {
  45         int typelen;
  46         char type[20];
  47         unsigned char sha1[20];
  48         const char *object, *type_line, *tag_line, *tagger_line, *lb, *rb;
  49         size_t len;
  50
  51         if (size < 84)
  52                 return error("wanna fool me ? you obviously got the size wrong !");
  53
  54         buffer[size] = 0;
  55
  56         /* Verify object line */
  57         object = buffer;
  58         if (memcmp(object, "object ", 7))
  59                 return error("char%d: does not start with \"object \"", 0);
  60
  61         if (get_sha1_hex(object + 7, sha1))
  62                 return error("char%d: could not get SHA1 hash", 7);
  63
  64         /* Verify type line */
  65         type_line = object + 48;
  66         if (memcmp(type_line - 1, "\ntype ", 6))
  67                 return error("char%d: could not find \"\\ntype \"", 47);
  68
  69         /* Verify tag-line */
  70         tag_line = strchr(type_line, '\n');
  71         if (!tag_line)
  72                 return error("char" PD_FMT ": could not find next \"\\n\"", type_line - buffer);
  73         tag_line++;
  74         if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
  75                 return error("char" PD_FMT ": no \"tag \" found", tag_line - buffer);
  76
  77         /* Get the actual type */
  78         typelen = tag_line - type_line - strlen("type \n");
  79         if (typelen >= sizeof(type))
  80                 return error("char" PD_FMT ": type too long", type_line+5 - buffer);
  81
  82         memcpy(type, type_line+5, typelen);
  83         type[typelen] = 0;
  84
  85         /* Verify that the object matches */
  86         if (verify_object(sha1, type))
  87                 return error("char%d: could not verify object %s", 7, sha1_to_hex(sha1));
  88
  89         /* Verify the tag-name: we don't allow control characters or spaces in it */
  90         tag_line += 4;
  91         for (;;) {
  92                 unsigned char c = *tag_line++;
  93                 if (c == '\n')
  94                         break;
  95                 if (c > ' ')
  96                         continue;
  97                 return error("char" PD_FMT ": could not verify tag name", tag_line - buffer);
  98         }
  99
 100         /* Verify the tagger line */
 101         tagger_line = tag_line;
 102
 103         if (memcmp(tagger_line, "tagger ", 7))
 104                 return error("char" PD_FMT ": could not find \"tagger \"",
 105                         tagger_line - buffer);
 106
 107         /*
 108          * Check for correct form for name and email
 109          * i.e. " <" followed by "> " on _this_ line
 110          * No angle brackets within the name or email address fields.
 111          * No spaces within the email address field.
 112          */
 113         tagger_line += 7;
 114         if (!(lb = strstr(tagger_line, " <")) || !(rb = strstr(lb+2, "> ")) ||
 115                 strpbrk(tagger_line, "<>\n") != lb+1 ||
 116                 strpbrk(lb+2, "><\n ") != rb)
 117                 return error("char" PD_FMT ": malformed tagger field",
 118                         tagger_line - buffer);
 119
 120         /* Check for author name, at least one character, space is acceptable */
 121         if (lb == tagger_line)
 122                 return error("char" PD_FMT ": missing tagger name",
 123                         tagger_line - buffer);
 124
 125         /* timestamp, 1 or more digits followed by space */
 126         tagger_line = rb + 2;
 127         if (!(len = strspn(tagger_line, "0123456789")))
 128                 return error("char" PD_FMT ": missing tag timestamp",
 129                         tagger_line - buffer);
 130         tagger_line += len;
 131         if (*tagger_line != ' ')
 132                 return error("char" PD_FMT ": malformed tag timestamp",
 133                         tagger_line - buffer);
 134         tagger_line++;
 135
 136         /* timezone, 5 digits [+-]hhmm, max. 1400 */
 137         if (!((tagger_line[0] == '+' || tagger_line[0] == '-') &&
 138               strspn(tagger_line+1, "0123456789") == 4 &&
 139               tagger_line[5] == '\n' && atoi(tagger_line+1) <= 1400))
 140                 return error("char" PD_FMT ": malformed tag timezone",
 141                         tagger_line - buffer);
 142         tagger_line += 6;
 143
 144         /* Verify the blank line separating the header from the body */
 145         if (*tagger_line != '\n')
 146                 return error("char" PD_FMT ": trailing garbage in tag header",
 147                         tagger_line - buffer);
 148
 149         /* The actual stuff afterwards we don't care about.. */
 150         return 0;
 151 }
 152
 153 #undef PD_FMT
 154
 155 int main(int argc, char **argv)
 156 {
 157         struct strbuf buf = STRBUF_INIT;
 158         unsigned char result_sha1[20];
 159
 160         if (argc != 1)
 161                 usage("git mktag < signaturefile");
 162
 163         git_extract_argv0_path(argv[0]);
 164
 165         setup_git_directory();
 166
 167         if (strbuf_read(&buf, 0, 4096) < 0) {
 168                 die("could not read from stdin");
 169         }
 170
 171         /* Verify it for some basic sanity: it needs to start with
 172            "object <sha1>\ntype\ntagger " */
 173         if (verify_tag(buf.buf, buf.len) < 0)
 174                 die("invalid tag signature file");
 175
 176         if (write_sha1_file(buf.buf, buf.len, tag_type, result_sha1) < 0)
 177                 die("unable to write tag file");
 178
 179         strbuf_release(&buf);
 180         printf("%s\n", sha1_to_hex(result_sha1));
 181         return 0;
 182 }